feat(ci): Make the revdep driver log's timing record durable and visible

[krlmlr]

Prepared with Claude Code (LLM-assisted).

Why _R_CHECK_TIMINGS_ is off, and stays off. The setting is inherited from revdep2 with a rationale that still holds: the two halves of a package run at different times next to different queue neighbours, so per-stage [user/elapsed] stamps differ by construction and would be pure noise in the very log the halves are compared through. The design compensated with check-half.sh's stamp() filter — every container line prefixed with elapsed seconds in driver.log — and the comment promised "nothing is lost".

That promise went quietly false in the container era: the driver log only ever lived in the runner's ephemeral work directory. The timeout analysis of run 33777134786 hit the wall this creates — for both-halves timeouts (ctmm, E2E, PortfolioTesteR) nothing was salvaged, and "where did the 1800 seconds go" had no answer in any artifact or log.

Three changes make the record real again, at a cost confined to the handful of failures per run:

• copy_check_output() now carries driver.log and status alongside every kept check directory, so anything salvaged brings its per-stage timeline with it.
• The failed side is salvaged too (salvage_side() in compare.R, wired into compare-one.R's failure branches — both sides when both fail). A killed check leaves a partial .Rcheck whose 00check.log lists every stage it completed; even a container that never ran leaves its driver log. Verified locally with simulated timeout work directories in both shapes.
• check-half.sh prints a failed half's stage timeline (the stamped * checking … lines, last 60) into the job log under a collapsible group, where GitHub's wall-clock timestamps stack on the elapsed stamps. Successful halves stay quiet.

After this, the next timeout's post-mortem is one grep — over the job log or the salvaged driver.log in the revdepx-report artifact — instead of an archaeology expedition.

• By submitting this pull request, I assign the copyright of my contribution to The igraph development team.

🤖 Generated with Claude Code

https://claude.ai/code/session_01UB7YutLzVWU7xCTYUvF3kF

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Generated by Claude Code